Fuel cells provide electricity from chemical oxidation-reduction reactions and possess significant advantages over other forms of power generation in terms of cleanliness and efficiency. Typically, fuel cells employ hydrogen as the fuel and oxygen as the oxidizing agent. The power generation is generally proportional to the consumption rate of the reactants.
A significant disadvantage which inhibits the wider use of fuel cells is the lack of a widespread hydrogen infrastructure. Hydrogen has a relatively low volumetric efficiency and is more difficult to store and transport than hydrocarbon fuels currently used in most power generation systems. One way to overcome this difficulty is the use of reformers to convert hydrocarbons to a hydrogen-rich gas stream that can be stored or used locally as a feed for fuel cells.
Hydrocarbon-based fuels, such as natural gas, LPG, gasoline, and diesel, require conversion processes to be used as fuel sources for most fuel cells. Current art uses multi-step processes combining an initial conversion process with several clean-up processes. The initial process is most often steam reforming (SR), autothermal reforming (ATR), catalytic partial oxidation (CPOX), non-catalytic partial oxidation (POX) or a combination thereof. The clean-up processes usually comprise a combination of desulphurization, high temperature water-gas shift, low temperature water-gas shift, selective CO oxidation, or selective CO methanation. Alternative processes include hydrogen selective membrane reactors and filters.
Despite the above work, there remains a need for a simplified fuel processing system for converting a hydrocarbon fuel to a hydrogen rich gas stream for use with a fuel cell. A practical obstacle facing any solution to this problem is the need to rapidly start-up the reforming reactor and the various combustion catalyst beds that may be used in the reforming process. Where autothermal reforming is desired, there is also the need to rapidly pre-heat the reforming reactants to their autothermal temperature(s) and to maintain those temperatures throughout the reforming process. Similarly, where steam reforming is used, the rapid and reliable generation of steam is also required.
The present invention addresses the need for a fuel reformer capable of rapid start-up and maintaining a more stable temperature profile during the operation of the reformer and that is capable of operating on low pressure fuel feeds.